Genetic and physical characterization of bacterial plasmids with an emphasis on the R6K multicopy, conjugative, ampicillin and streptomycin resistant plasmid. The overall objectives are an understanding of its replication transfer and genetic expression. The specific aims include the analysis of regulation of the multicopy plasmid state, its interrelationship with properties of incompatibility, the ability to be eliminated and to mobilize other non-conjugative plasmids. The factors controlling the genetic expression resulting from the cointegration of more than one regulatory system on a single molecule will be explored. Emphasis will also be placed on the analysis of the control of mobilization. The investigations will involve the use of restriction enzymes for mapping and joining segments of independent plasmids, and their selection by transformation. Analysis will also be approached by the use of electron microscopy heteroduplexing.